I have a broadband cable connection. This is the only computer connected to it and has an 10/100Mb ethernet card. After I totally formatted the hard disk and installed XP pro (insted of 98 I had) the connection started acting weird. Sometimes the speed is around 30kb/s, usually around 5kb/s, but then it starts slowing down (while downloading a page) and can go down to 20b/s!! I ran a test which showed that the most of the times the connection was ok, but then once it said that the gateway lost 25% of data somewhere? There´s no conflicts according to XP in my computer. I´m no expert, so please could someone give me some simple explenation?

try releasing and renewing your IPCONFIG. if that doesn't help, there are registry mods that can be made to the IP block size but, before doing that, you may want to just call tech support from your ISP as they may be having problems on their end.

The problem might be also after the ISP, I would download this program called neotrace it will tell which hop is giving you the problem (it's a GUI traceroute program). The problem might be at the NAP level or a peering problem between the autonomous systems.

also double check the cables. i had a friend who had random slow downs with his cable internet and he had a faulty ethernet cable.